Process and apparatus for pressurizing lower extremities of a patient during ventricular diastole



Feb. 14, 1967 c. DENNIS 3,303,841

PROCESS AND APPARATUS FOR PRESSURIZING LOWER EXTREMITIES OF A PATIENTDURING VENTRICULAR DIASTOLE Filed June 18, 1964 IZ HINT CLARENCE DENNIS4 4 United States Patent 3,303,841 PROCESS AND APPARATUS FORPRESSURIZING LOWER EXTREMTHES OF A PATENT DURHNG VENTRICULAR DIASTGLEClarence Dennis, Pelharn Manor, N.Y., assignor to the United States ofAmerica as represented by the Secretary, Department of Health, Educationand Welfare Filed June 18, 1964, Ser. No. 377,178 9 Claims. (Cl.128--24) My invention relates to the process of and apparatus forreducing the work of the left ventricle of the heart by forcing bloodback into the aorta and great arterial vessels through externalcompression of the body during ventricular diastole and relieving thisback pressure when the left ventricle is emptying to the aorta.

External compression of a part of the body will express a volume ofblood larger than the volume of blood pumped in one stroke of the heart,this expressed blood being forced back into the aorta and great arterialvessels to reduce ventricular work while maintaining satisfactory bodyperfusion during ventricular diastole.

The principle of counterpulsation for support of the failing heart isknown. Large cannulas are placed in the femoral vessels directedproximally and blood is removed from the aorta while the ventricle isejecting blood into the aorta, thus permitting contraction of the leftventricle against a lower than normal pressure and thereby reducing thework of the left ventricle. An external pump is used to return blood tothe aorta as soon as the end of the ventricular contraction has occurredand the aortic valve is closed. During the period in which the leftventricle is filling from the left atrium and lungs with the aorticvalve closed, blood is returned to the aorta in suflicient volume toraise the pressure to a level equivalent to the peak pressure observedunder control circumstances. In this manner, the amount of work requiredof the left ventricle is reduced while maintaining a satisfactoryperfusion pressure in the arterial tree to take care of the needs of theentire body.

My invention avoids the necessity for the trauma of making incisions andputting cannulas into blood vessels and avoids the necessity ofadministering heparin to prevent clotting. A particularly effectivetechnique involves squeezing blood out of the caudal arterial tree toproduce a rise in aortic pressure during ventricular diastole andrelieving the caudal arterial tree when the left ventricle is emptyingto the aorta. A surveillance means, such as an electrocardiograph, canthrough a synchronizing means operate a compression means to compressand release the hind quarters and pelvis and thereby cyclically squeezeblood from the arterial tree in the desired synchronization with thecardiac cycle.

Other objects and advantages will become apparent in the course of thefollowing detailed description, wherein:

FIG. 1 is a diagrammatic view of the human body and the apparatus of myinvention;

FIG. 2 is a graphical showing from top to bottom of pressures in theleft ventricle, aortic arch, and compression means, and also of thecardiac cycle as shown on the electrocardiograph; and

FIG. 3 is a perspective View of a flexible envelope used in myinvention.

Referring now to FIG. 1, it will be seen that the body 15 is placed in acontainer 17 having an opening 18 therein which closely conforms to thelower torso of the body, the legs, hind quarters and pelvis of the bodybeing housed within the container. The container 17 includes a two-piececover 16 which forms opening 18 and which is tightly clamped to thewalls of the container by swing clamps 19. The container includes anenvelope 2%) of flexible material, such as mil polypropylene, which33%,841 Patented Feb. 14, 1967 has peripheral outer walls 22 whichconform to the inner confines of the container, the envelope 20 alsohaving inner walls 24 which define a cavity for the part of the bodywithin the container. As shown, the envelope 20 takes the form of whatmight be considered a pantaloon type garment, the material of theenvelope completely contacting and engirdling the legs and lower torsoof the body. A filling connection 26 is provided for filling theenvelope with water, a suitable vent 28 being provided for exhaustingair from the envelope as the envelope is filled. A flexible air bladder30 is suitably positioned within the container 17 and connected througha solenoid air control valve 32 to a pressured air source such as tankand supply line 34, these elements making up a pressure means. Thesolenoid air control valve 32 is electrically connected to asynchronizing means 36 which in turn is connected to a surveillancemeans 38. When the surveillance means 38, which is electricallyconnected to the body, indicates the closing of the aortic valve, thesynchronizing means 36 responds to this signal and actuates the solenoidvalve 32 to admit air to the bladder 30 and to inflate the bladder andthereby increase the pressure in the bladder to a predetermined pressureas determined by the pressure setting and relief valve unit such as thepressure controller 40. When the bladder 3% is inflated as shown in FIG.1, the pressure within the container is increased due to theincompressibility of the water in the envelope 20 and the legs and lowertorso of the body part are compressed, thereby squeezing blood from thecaudal arterial tree 42 back into the aorta 44 to establish asatisfactory perfusion pressure in the arterial tree. It will beunderstood that an electrocardiograph with voltage taps 39 can serve asthe surveillance means 38 and that the synchronizing means 36 can takethe form of an electronic timing device which will synchronize thecompression means 46 with the cardiac cycle. It has been found that witha human being in a half pressure suit engirdling the lower torso andlegs, approximately 7.5 gm./kg. of body Weight can be expressed from thelegs and pelvis at a pressure of mm. Hg. The synchronizing means 36 inresponse to a signal from the surveillance means 38 identifying theopening of the aortic valve will cause the opening of the solenoid valve32 and thereby exhaust the high pressure air from the bladder 30 torelieve the pressure in the container and relieve the pressure in thecaudal arterial tree and the aorta to enable emptying of the ventricleagainst a lower aortic pressure.

It has been found that the use of an incompressible fluid to transmitthe pressure developed by a compression means provides a fast and soundtechnique for accomplishing compression of the body part within theshort time period afforded by the cardiac cycle. Suitably sized airfittings and air volumes are required to substantially instantaneouslyproduce the required predetermined pressure in the bladder and toaccomplish relief of this pressure in synchronism with the cardiaccycle. Fluids employed have been air and water although other gases andliquids may be substituted. The liquid should have a specific gravityequal to or greater than the blood when the body part is in the somewhatvertical position to prevent a top to bottom closing of the arteries inthe body part.

It will be understood that the flexible polypropylene envelope 20 ofFIG. 3 provides a feasible method of enveloping the body; a simple pantgarment might also be used with the container 17 being made fluid tightand equipped with the necessary connections.

The air-liquid combination provides a fluid system capable ofsubstantially instantaneous response to signals from the surveillancemeans 38 and synchronizing means 36.

An application of my process and apparatus to an 11 kg. dog involved arigid container somewhat similar to that shown in FIG. 1 and having theopening 18 at one end precisely formed to fit the contour of the dogjust above the pelvis. The envelope pressure was produced by a -14p.s.i. pressure line with an air reservoir tank and a /4 inch solenoidcommunicating through a 1 inch iron pipe connection to a heavy rubberbladder in the bottom of the encasing box. The solenoid was activatedthrough an electronic circuit so as to provide external pressure ofpredetermined duration, pressure level, or lag after initiation ofventricular contraction. The electronic circuit was triggered by the Rwave of the QRS complex of the electrocardiograph; the beginning rise inthe left ventricular pressure may also be used for triggering theelectronic circuit. A tracheal tube was routinely placed for utilizationof a Jefferson respiration and the left chest was opened for directplacement of polyethylene catheters (0.054 inch in external diameter)into the left ventricle and into the aorta. The electrocardiograph andpressures in the left ventricle, the aortic arch, and the compressionenvelope were recorded on a 4-channel Sanborn recorder, the recordingsbeing shown in FIG. 2. Intra-abdominal pressure and venous pressure mayalso be recorded where desired. FIG. 2 shows typical recordingsidentifying changes in left ventricular and aortic pulse waves withexternal counterpulsation applied to the hind quarters. The leftventricular component of the aortic pressure curve is reduced from 112mm. Hg to 90 mm. Hg. The left ventricular peak pressure is lowered from112 mm. Hg to 100 mm. Hg. The imposed aortic peak pressure is 114 mm.Hg. Paper speeds: slow-O.25 mm./sec.; fast mm./sec. Use of a slow paperspeed permits perspective as to relatively slow responses. For 5 to 6seconds there was a rise in left ventricular and aortic arch pressure,followed by a mm. Hg drop, with resumption in about 30 seconds of a peakpressure in diastole slightly greater than the control systolicpressure. The left ventricular pressure rose late in the first 30seconds of external counterpulsation to a level 12 to 15 mm. Hg belowthe control left ventricular systolic pressure. At the end of periods ofexternal counterpulsation, the changes in left ventricular pressure wereessentially mirror images of those at the beginning. The aortic archpressure changes were slower to revert to control levels, but did so in1% min.

The electronically controlled external counterpulsator unit of myinvention has proven capable of raising the envelope pressure to 150 mm.Hg in 0.04 second and of permitting it to drop to the atmospheric levelin 0.06 second. It has been possible to lower the peak aortic pressure 5to 10 mm. Hg, to raise the aortic pressure during left ventriculardiastole to levels higher than the control systolic pressure, and tolower the timetension index 8 to 10 percent. The time-tension index is achief determinant of the work of the heart as measured by oxygenconsumption and is determined by securing the product of the pressureagainst which the left ventricle must eject blood into the aorta and theduration of that ejection. Pressure tracings in an 11 kg. dog with pulserate of 111 were obtained with 10 p.s.i. air pressure, a lag after the Rwave of 0.12 sec. and a duration of compression of 0.32 see. FIG. 2indicates the results of the application of my method and process tosuch a dog. It also has been noted that some reduction in time-tensionindex was obtained even though the envelope pressure peak was less thanthe systolic blood pressure. External counterpulsation as abovediscussed indicates that the effect on intra-abdominal and centralvenous pressure was very small.

The above application of my invention to a dog demonstrates thatsufficient blood can be expressed from the buttocks and hind legs of thedog to be effective in lessening the time-tension index of the leftventricle, while providing a peak aortic pressure during leftventricular diastole equal to the control systemic blood pressure. Thearterial blood expressible from the caudal arterial tree of a dog is ofthe order of magnitude of 3 ml./kg. of body weight. At pressures below50 mm. Hg, much larger extremity weight losses occurred, these beingattributed to expression of venous blood and lymph.

The fluid pressure developed in my apparatus is preferably in the rangeof 2 to 5 p.s.i. It will be noted that the anatomical and physiologicalcharacteristics of the human arterial system and the arterial system ofa dog are somewhat similar, even though the dog normally has a higherblood pressure and faster pulse than the human.

As noted in the drawing, the body is preferably placed at an inclinationof about 20 from the horizontal with the heart approximately at a levelat or above the highest level of the fluid in the container, the fluidbeing oriented by the container to transmit pressure to the buttocks andto the lower torso preferably at and below the upper margin of the bonypelvis thereby to minimize compression of the internal organs. Theinclination of the body may vary from patient to patient, the degree ofinclination being similar to that presently employed in treatingpatients with acute left heart failure, the inclination beingadvantageous in that it positions the heart and upper part of the bodyat a level which tends to compensate for the increased pressure in theblood system produced by the liquid in the container in unpressurizedcondition.

While in an emergency, water may be used, it is advantageous that thefluid have a higher specific gravity than blood, satisfactory fluidsbeing, for example, salt solutions such as magnesium sulfate solutionswhich have a specific gravity slightly higher than blood.

It will be understood that similar apparatus may be applied to one orboth of the arms for compressing more peripheral portions of the distalarterial tree and suitably synchronized with the cardiac cycle toreplace or supplement back pressure produced through compression of thelower torso, the arms being particularly suitable in that they providegreater volume-per-weight percentage of blood as compared to the lowertorso. As seen in FIG. 1, a suitable arm container 50 schematicallyshown may be employed, this container being interconnected with thecontrol and power components similar to container 17.

The exact synchronization of the solenoid valve varies somewhat fromindividual to individual and is influenced by the flexibility of thewalls of the arterial tree and by the length of the great arteries. Inthe laboratory the development of the pattern of synchronization hasbeen based upon pressure tracings from the ascending aorta and the lagafter the QRS complex of the electrocardiogram, and the electroniccircuitry is designed to permit adjustment of the duration of this lagand the duration of compression to the characteristics of theindividual. In the clinical case it is uncomplicated to pass a fineflexible catheter through a hypodermic needle passed into the brachialor other artery to the aortic arch for verification of thesynchronization. This requires neither incision nor anticoagulants.

I claim:

1. The process of reducing the work of the left ventricle in the heartcomprising surveillance of the cardiac cycle to identify the openedcondition and the closed condition of the aortic valve, externallycompressing the body when the aortic valve is in the closed condition toforce blood back into the aorta to establish a satisfactory perfusionpressure in the aorta and arterial tree, relieving the compression whenthe aortic valve is in the opened condition to permit contraction of theleft ventricle against a lowered aortic pressure.

2. The process of reducing the work of the left ventricle in the heartcomprising surveillance of the cardiac cycle to identify the opening andclosing of the aortic valve, externally compressing the hind quartersand pelvis of the body when the aortic valve is closed to force theblood from the caudal arterial tree back into the aorta to establish asatisfactory perfusion pressure in the aorta and arterial tree,relieving the compression when the aortic valve is open to permitcontraction of the left ven tricle against a lowered aortic pressure.

3. A device for reducing the Work of the left ven tricle in the hearcomprising surveillance means for identifying the opening and closing ofthe aortic valve, compression means for compressing the body,synchronizing means operatively interconnecting said surveillance meansand said compression means for causing the compression means to compressthe body when the aortic valve is closed to force blood into the aortato establish a satisfactory perfusion pressure in the aorta and arterialtree, and for causing the compression means to relieve the compressionwhen the aortic valve is open to permit contraction of the leftventricle against a lowered aortic pressure.

4. A device as defined in claim 3 and wherein said compression meansincludes a container having an opening therein for admitting and housinga part of the body, fluid surrounding said part of the body and fillingthe container, and pressure means acting on said fluid to raise andlower the pressure of the fluid in the container in predeterminedresponse to signals from said synchronizing means.

5. A device as defined in claim 3 and wherein said compression meansincludes a rigid container having an opening therein for admitting apart of the body, an envelope of flexible material positioned withinsaid container and having peripheral outer walls conforming to saidcontainer and inner walls, said inner walls defining a cavity in saidenvelope for the body part, incompressible fluid filling said envelopethereby causing said outer walls to contact said rigid container andsaid inner walls to contact and engirdle the body part, pressure meansacting on said incompressible fluid to raise and lower the pressure ofthe fluid in the container in predetermined response to signals fromsaid synchronizing means.

6. A device as defined in claim 5 and wherein said pressure meansincludes an inflatable flexible bladder positioned within said envelopeand gas means connected to said bladder to inflate and deflate saidbladder with gas in predetermined response to signals from saidsynchronizing means.

7. The process of reducing the work of the left ventricle in the heartcomprising surveillance of the cardiac cycle to identify the opening andclosing of the aortic valve, externally compressing the caudal arterialtree when the aortic valve is closed to force blood back into the aortato establish a satisfactory perfusion pressure in the aorta and arterialtree, relieving the compression when the aortic valve is open to permitcontraction of the left ventricle against a lowered aortic pressure.

8. The process of reducing the Work of the left ventricle in the heartcomprising surveillance of the cardiac cycle to identify the opening andclosing of the aortic valve, externally compressing the distal arterialtree when the aortic valve is closed to force blood back into the aortato establish a satisfactory perfusion pressure in the aorta and arterialtree, and relieving the compression when the aortic valve is open topermit contraction of the left ventricle against a lowered aorticpressure.

9. A device as defined in claim 3 and wherein said container ispositioned at an inclination from the horizontal to place the heart atabout the level of the highest level of liquid in the container.

References Cited by the Examiner UNITED STATES PATENTS 4/1954 Erickson128-24 X 9/1954 Fuchs 128-44

1. THE PROCESS OF REDUCING THE WORK OF THE LEFT VENTRICLE IN THE HEARTCOMPRISING SURVEILLANCE OF THE CARDIAC CYCLE TO IDENTIFY THE OPENEDCONDITION AND THE CLOSED CONDITION OF THE AORTIC VALVE, EXTERNALLYCOMPRESSING THE BODY WHEN THE AORTIC VALVE IS IN THE CLOSED CONDITION TOFORCE BLOOD BACK INTO THE AORTA AND ARTERIAL TREE, RELIEVING PERFUSIONPRESSURE IN THE AORTA AND ARTERIAL TREE, RELIEVING THE COMPRESSION WHENTHE AORTIC VALVE IS IN THE OPENED CONDITION TO PERMIT CONTRACTION OF THELEFT VENTRICLE AGAINST A LOWERED AORTIC PRESSURE.